Chapter 3. Dialogs

A dialog is defined by its usage. If a form is the application's main window, it's a window, not a dialog. However, if a form pops up in response to a user request for service, such as a request to open a file, and stops all other user interactions with the application, it's a dialog (a modal dialog, specifically ).

However, things get a little murky when we consider modeless dialogs. They don't stop the user from interacting with the rest of the application, but they do provide a means of interaction outside the main window.

What makes things a bit murkier is the WinForms terminology. Standard dialogs are exposed by the XxxDialog family of components, such as the FileOpenDialog. Most of these components support only modal activation using ShowDialog, but a couple of them support modeless activation using Show. In contrast, custom dialogs are classes that derive from the Form base class and can be shown modally or modelessly based on whether they're activated using ShowDialog or Show.

No matter how a dialog is defined, this chapter covers things you'd normally think of as dialog- related issues, including standard dialogs, custom forms to be used as dialogs, modal and modeless activation and lifetime, transferring data in and out, validating user-entered data, and providing help. To aid you in making the transition to the unification of dialog-like functionality with forms, we don't use the term "dialog" except when referring to the standard dialog components.